Liner for a wellbore

ABSTRACT

A liner for a wellbore having a sidewall in which one or more nozzles are formed is described, wherein the one or more nozzles are plugged by temporary plugs. Also described is a method of completing an open hole well that penetrates a subterranean formation in which a liner having a sidewall in which one or more nozzles are formed, wherein the one or more nozzles are plugged by temporary plugs, is deployed in the well such that the nozzles communicate with the formation.

The present invention concerns liners for wellbores. The present invention is also directed to a well completion method for displacement from non-aqueous fluid to aqueous fluid using temporary plugged nozzles.

BACKGROUND

Oil well instabilities and the resultant production losses have been studied and methods to limit and reduce such losses have previously been taught. These methods have been applied to oil wells.

European Patent No. 2 253 798 to Nguyen (“Nguyen”) teaches a method of stimulating production flow from a formation. The method includes placing an acid fluid into the formation area to be stimulated to partially dissolve a portion of the area of the formation. The application discusses the types of acids to be used for this process and specifically states that aqueous based acids are best suited. Once the formation has been degraded (to a degree) a consolidating fluid is then injected into the formation. The consolidating fluid is chosen from a type of binding fluid, such as resin composites, tackifying agents and other fluids which cause agglomeration of fine, solid particles. The next step includes washing the area with a fluid to remove the agglomerated materials. The wash fluid may be fresh water. Further steps involve placing a fracturing fluid into the area of the subterranean formation to create, or at least extend, a fracture therein.

U.S Patent Application No. 2014/0224807 to Ramon (“Ramon”) teaches of a plug arrangement wherein the plug is configured to lead, or follow a hardenable material (such as cement) which is being pumped through a tubular body. The plug includes one or more portions which are configured to weaken when exposed to an activation fluid. The material in this instance is a controlled electrolytic metallic material. The plug further includes a plurality of plugs nested within one another, wherein the leading plug is in sealing engagement with the walls of a tubular body. The activation fluid used for degrading the electrolytic material can include brine, acid, and aqueous fluid or combinations thereof. The nested plug may also include a bore, to allow activation fluid to penetrate and effectively reach the leading plug. The weakening of the plug portions specifically includes dissolving one or more of the portions.

U.S. Pat. No. 3,924,677 to Prenner et al. (“Prenner”) teaches of a device used in the completion of an oil well. The device is a conduit which extends through the sidewall of a well casing. The conduit is held in a retracted position in the sidewall from the interior of the casing by a friction sleeve formed of PVC. The opposing end of the conduit is shielded, to a degree, from the outer environment by a sacrificial cup body. The ends of the conduit are sealed with salt stoppers which are shielded from fluids. Once the casing has been sunk to the required depth and the cement plug has been formed, the outer protective cup (formed of cast iron) is manually broken to expose the salt stoppers within the bore of the conduit. The casing is swabbed which will cause the salt plugs to dissolve to open the member from both sides. Passage between the strata and the interior of the well casing will then be possible.

Aviles et. al (“Dissolvable Plug and Perf system eliminates mills-out in multistage stimulations”; AVILES, Isaac; DARDIS, Michael; JACOB, Gregoire; Society of Petroleum Engineers, Journal of Petroleum Technology, June 2015; “ALVIES”) teaches of a plug and nozzle arrangement for plugging and perforating a wellbore liner wherein the plug seat is dissolvable. The new approach replaces mechanical intervention for removing plugs. It is taught that seat assemblies serve the purpose of plugs and dissolve in a controlled manner after the stimulation has been performed. This process will release the ball and leave a full-bore inner diameter. Additionally the disclosure teaches of a dropping an additional seat to seal the nozzle. The seat matches the geometry of the receptacle to create a metal-on-metal seal. A ball is then dropped from the surface to land in the seat and complete the isolation from the previous zone. After stimulation the seats are dissolvable allowing for immediate production.

U.S. Pat. No. 9,151,143 to Holderman et al. (“Holderman”) teaches of a sacrificial dissolvable plug. The plug is used in series with a flow restrictor which is disposed in a fluid pathway between the exterior of a wellbore and the interior of the wellbore. The plug is configured to be at least partially dissolvable when contacted by a fluid. The fluid comprises a chemical configured to dissolve the plug.

U.S. Pat. No. 9,068,429 to Mailand et al. (“Mailand”) teaches of a dissolvable tool which is formed as a body which includes at least one portion thereof which is configured to dissolve in a fluid. The body includes a barrier and the body is able to move through a structure, preferably a conduit. The body (and barrier) seal the conduit, as the body moves there through. Common techniques to remove a sealing plug of this kind include milling or drilling out the plug.

Turning to Prenner which discloses a combination of a mechanical and non-intervention technique for removing a plug. A solid and a salt plug are housed within a translating hollow member in a protective casing. The hollow nature of the member is protected from future cementing operations by being solid on the side closest to the inner diameter of the protective casing and having a salt plug on the opposing side. The sliding member is extended from the protective casing to the wellbore by means of pressure and then cemented in place. Following cementation, the solid plug within the hollow member is removed by mechanically means with a downhole assembly including a bit deployed within the casing. The salt plug within the hollow member is then exposed to a fluid, which results in the dissolving of the salt plug to take place leaving a hollow conduit connecting the inside of the casing with the wellbore through the cement. This then allows for flow passage from the wellbore, through the extended hollow member into the conduit. The use of fluids to dissolve a plug is therefore known. Prenner does not disclose the use of temporary plugs deployed within nozzles within the sidewalls of a liner that do not extend to the wellbore.

Aviles teaches of a dissolvable object placed in the path of a conduit. The Aviles disclosure differs from the previously cited application in that the ‘plug’ itself is not dissolved, but instead the seat in which the ‘plug’ (ball) is located dissolves. The application provides an alternative approach to un-obstructing a flow path through a conduit by dissolving the flow restrictor.

Mailand teaches of a body which includes a dissolvable portion, and a barrier portion. The barrier portion being in sealing engagement with the interior of a conduit. Much like Aviles, a portion of the flow restricting object is dissolvable so as to provide flow passage through a conduit.

Turning to Holderman, the disclosure thereof teaches of a screen assembly with a sacrificial plug placed in a sidewall of a conduit and in conjunction with a flow restrictor run in series to the sacrificial plug. The sacrificial plug is dissolvable when contacted with a chemical fluid, to provide passage between the interior and exterior of a well bore (through the sidewall, flow restrictor and screen assembly). Holderman does not disclose the use of plugs, in combination with nozzles which extend through sidewalls of a liner. Holderman also does not disclose the dissolution of the plug without the use of chemicals. Holderman does not disclose the use of dissolvable plugs without the use of a screen assembly.

SUMMARY OF THE INVENTION

The present application teaches of a process for removing the temporary plugs, fitted to nozzles, in a liner. The process is referred to as intervention free, which means that physical intervention (such as blasting or shooting hardened steel bullets) is not used.

Current methods include the deployment of a work string followed by the deployment of a pre-drilled liner to final position. Pre-drilling the liner is well specific, and requires a lot of time. Additionally the process requires an inner string to be deployed.

The current application looks to overcome the need for a work string and an inner string to displace the plugged nozzles.

In order to achieve one or more of these objectives the present invention provides a liner for a wellbore having a sidewall in which one or more nozzles are formed, wherein the one or more nozzles are plugged by temporary plugs. A liner in the sense of this invention is thus a wellbore equipment, especially oil wellbore equipment. Such a liner may act as a pipe and forms a conduit. A sidewall or jacket of the liner is thus the sidewall of a pipe or conduit and has a proximal end and a distal end such that medium can be transported through the liner from the proximal end to the distal end and/or vice versa. The temporary plugs are preferably removable by using a plugging medium that dissolves upon exposure to elevated temperature and/or an activation fluid, preferably an aqueous fluid. A plugging medium which dissolves in an activation fluid and especially in an aqueous fluid can for example be a salt. In an alternative preferred embodiment the temporary plugs are mechanical plugs that are removable by application of pressure cycles. It is further preferred that the inventive liner comprises a liner top packer which isolates the liner top such that during operation all fluid flow is through the nozzles. It is also preferred that the inventive liner comprises a liner shoe and a liner shoe shut off device, wherein the liner shoe shut off device allows circulation during displacement operations and subsequently isolates the liner shoe. In such a preferred embodiment the liner shoe shut off device can be shut by electronics activated by timer, Radio-frequency identification (RFID), pressure, flow or any combination of these. Alternatively it can be shut by mechanical means using either a sleeve mechanically actuated by intervention means, a dart/ball dropped from surface to mechanically isolate the shoe or a combination of both.

In order to achieve one or more of the above-mentioned objectives the present invention further provides a method of completing an open hole well that penetrates a subterranean formation in which a liner having a sidewall in which one or more nozzles are formed, wherein the one or more nozzles are plugged by temporary plugs, is deployed in the well such that the nozzles communicate with the formation. It is preferred that a liner shoe shut off valve is deployed to allow initial fluid displacement through the liner with plugged nozzles. It is further preferred that after positioning of the liner the temporary plugs are removed from the nozzles.

In order to achieve the above-mentioned objectives the application further teaches the use of temporary plugs which can be removed by non-physical means or intervention free methods. This is achieved by using a plug made from a specific material or medium. The medium is ultimately dissolved, which provides for production flow through the nozzle, which is no longer obstructed. The dissolving of the plug is due to the nature of the medium and the exposure of this medium to temperature or activation fluid (typically an aqueous fluid). A mechanical plug may be used, and removed by application of pressure cycles.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described with reference to the accompanying drawings of which:

FIG. 1 shows a Base Case Well Design with standard nozzles in liner;

FIG. 2 shows a Base Case Well Design showing displacement string required for displacing from non-aqueous fluid to aqueous fluid.

FIG. 3 shows the progression of design from base case (left embodiment) to embodiments according to the present invention (middle and right embodiment).

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to the field of oil well drilling and more particularly to oil well completion and liners for achieving such a completion. The process in which the inventive liner can be advantageously used preferably involves providing a pre-punctured liner having plugged nozzles extending through the punctured holes. Once the liner is positioned, the temporary plugs allow for displacement of the wellbore from non-aqueous fluid to aqueous fluid. Thereafter the plugs are removed from the nozzles to provide unobstructed production and injection flow.

The present invention thus teaches in a preferred embodiment a method of completing an open hole well that penetrates a subterranean formation to control the production of oil from and injecting acidizing fluid to the formation. The well is provided with nozzles that extend through the liner and communicate with the formation. The nozzles provide negligible pressure drop in a steady state production scenario while in a transient high rate injection scenario sufficient pressure drop is achieved to allow for even distribution of injection fluids. Temporary plugs are located in the nozzle throat such that initially the nozzles act as a blank piece of pipe. A liner shoe shut off valve is deployed to allow initial fluid displacement through the liner with plugged nozzles. The liner with temporary plugs is deployed in the well in a non-aqueous fluid. The temporary plugs in conjunction with other components allow for displacement of non-aqueous fluids through the casing/liner during deployment to assist with reaching final placement depth. Once the liner is positioned, the temporary plugs allow for displacement of the wellbore from non-aqueous fluid to aqueous fluid. Thereafter, the temporary plugs are removed from the nozzles to provide unobstructed production and injection flow paths to the formation and unobstructed internals of the casing/liner for future intervention. Temporary plugs may be removed by a variety of intervention free methods such as: temperature dissolved materials, aqueous fluid dissolved materials, pressure actuated valves. Subsequent to the aqueous fluid displacement operations, a shut off valve isolates the shoe and ensures all future production and injection fluids pass through the nozzles once the temporary plugging mechanism is removed. A delayed actuated liner top packer is set once the aqueous fluid displacement operation is complete.

Current methods for displacing the pre-drilled liner from non-aqueous to aqueous fluid typically require deployment of a work string following deployment of the pre-drilled liner to final position. Such methods require significant operational time to manage the work string within the drilling rig structure and for physical deployment.

Pre-drilling of the liner is well specific and performed such that it provides negligible pressure drop in a steady state production scenario while in a transient high rate injection scenario sufficient pressure drop is achieved to allow for even distribution of injection fluids.

Alternate methods for the same displacement operation are to deploy the work string as an inner string within the pre-drilled liner. This method is not applicable in extended reach applications due to the higher weight of the liner negating ability to deploy to final position through increased drag.

The method according to the present invention enables displacement operation to take place through the pre-drilled liner without a subsequent work string deployment run nor the use of an inner string.

Preferred components that make this method achievable are described below:

Liner top packer with delayed activation (until after aqueous fluid displaced). Once set, this packer isolates the liner top ensuring all fluid flow is through the nozzles.

Liner shoe shut off device that allows circulation during displacement operations and subsequently isolates the shoe for the life of the well. Once isolated all fluid flow is through the nozzles. Device can be actuated shut by electronics activated by timer, RFID, pressure or flow. Alternatively a device that is shut by mechanical means using pressure, actuation dart/ball or combination of both.

Temporary plugged nozzles which are removed once the aqueous fluid displacement operations are completed. Temporary plugs can be removed by using a plugging medium that is dissolved with time and exposure to temperature and/or an activation fluid (typically an aqueous fluid) or a mechanical plug that is removed by application of pressure cycles. Temporary plugs must be designed to withstand differential pressure generated by the displacement operations across the device and provide sufficient time delay before removal to complete same.

A number of different temporary plugs may be utilized to execute the stated method.

Temporary plugs can be removed by using a plugging medium that is dissolved with time and exposure to temperature and/or an activation fluid (typically an aqueous fluid) or a mechanical plug that is removed by application of pressure cycles. Plugs would be required to withstand suitable differential pressure to allow displacement of the non-aqueous fluid with aqueous fluid at high rate. If temperature or activation fluid dissolution method is utilised, sufficient delay is required to enable deployment of the liner in an extended reach application.

The method described provides significant operational time and cost savings over the historical method. In addition the method described allows the pre-drilled liner to be washed, floated and/or reamed to total depth in extended reach applications. The nature of the temporary plugging of the nozzles in conjunction with the shut off shoe and liner top may also allow for the liner to be utilised as a tested barrier for upper completion operations. 

1. Liner for a wellbore having a sidewall in which one or more nozzles are formed, wherein the one or more nozzles are plugged by temporary plugs.
 2. The liner according to claim 1 wherein the temporary plugs are removable by using a plugging medium that dissolves upon exposure to elevated temperature and/or an activation fluid, preferably an aqueous fluid.
 3. The liner according to claim 1 wherein the temporary plugs are mechanical plugs that are removable by application of pressure cycles.
 4. The liner according to claim 1 which comprises a liner top packer which isolates the liner top such that during operation all fluid flow is through the nozzles.
 5. The liner according to claim 1 which comprises a liner shoe and a liner shoe shut off device, wherein the liner shoe shut off device allows circulation during displacement operations and subsequently isolates the liner shoe.
 6. The liner according to claim 5 wherein the liner shoe shut off device can be shut by electronics activated by timer, RFID, pressure or flow.
 7. The liner according to claim 5 wherein the liner shoe shut off device can be shut by mechanical means using pressure, actuation dart/ball or a combination of both.
 8. A method of completing an open hole well that penetrates a subterranean formation in which a liner having a sidewall in which one or more nozzles are formed, wherein the one or more nozzles are plugged by temporary plugs, is deployed in the well such that the nozzles communicate with the formation.
 9. The method according to claim 8 wherein a liner shoe shut off valve is deployed to allow initial fluid displacement through the liner with plugged nozzles.
 10. The method according to claim 8 wherein after positioning of the liner the temporary plugs are removed from the nozzles. 